1. Field of the Invention
The present invention relates to a motor, and more particularly, to a motor in which an overhang is protruded from the circumference of a rotor core facing a stator in the axial direction.
2. Description of the Related Art
FIG. 1 is a perspective view illustrating a conventional motor, FIG. 2 is a plan view of the conventional motor, and FIG. 3 is a sectional view taken along the line A-A in FIG. 1.
The conventional motor shown in FIG. 1 to 3 is an inner rotor motor in which a rotor 20 is rotatably installed in a stator 10 by a predetermined gap G and rotated due to the electromagnetic interaction between the rotor 20 and the stator 10.
The stator 10 includes a ring-shaped yoke 12, a plurality of teeth 14 radially arranged on the inner wall of the yoke 12, and coils 16 wound around the teeth 14 and electrically connected to an external electric power source.
Here, the combination of the yoke 12 and a plurality of teeth 14 is referred to as a stator core. The stator core is manufactured by laminating a plurality of electric steel sheets having the same plane as that of the stator core.
The rotor 20 includes a rotor core 22 disposed in the stator 10 to rotate while keeping the predetermined gap G and a plurality of magnets 24 attached to the rotor core 22 in the radial configuration.
The rotor core 22 is formed by laminating a plurality of electric steel sheets having the same plane as that of the rotor core 22.
Particularly, in the above-mentioned rotor 20, when the area of the rotor 20 facing the stator 10 is large, the quantity of effective magnetic flux orthogonal to the stator 10 is increased so that the performance of a motor is improved. Thus, the rotor 20 is longer than the stator 10 in the axial direction, and this is called “Overhang Effect”.
In order to achieve the overhang effect in the conventional motor, only the outer circumference of the rotor core 22 is longer than the stator 10 in the axial direction. However, since the electric steel sheets have a two-dimensional structure, overall rotor 20 is longer than the stator 10 in the axial direction, and manufacturing costs for the improvement of the motor are increased.
Moreover, in order to achieve the overhang effect in the conventional motor, since the rotor 20 is longer than the stator 10 in the axial direction, entire volume of the conventional motor is increased, or in the event of restricting the entire size of the conventional motor, the stator 10 becomes relatively smaller. As a result, there arises a counter effect that core loss of the stator 10 is increased.